The present invention relates generally to a light source, and relates more particularly to a light emitting diode (LED)-based signal head.
Traffic lights, rail lights and other signal heads often suffer from poor light uniformity across the lens surface. Poor light uniformity is distracting and is typically considered objectionable. The Institute for Transportation Engineers (ITE) has recently set a lens luminance uniformity requirement for a round traffic ball of ten to one. This means that no area of the lens can be ten times brighter than any other area of the lens.
In some traffic light designs, a large number of low-power LEDs are arranged uniformly across the traffic front of the signal head. This gives a “pixelated” appearance which is often objectionable. In another design, a small number of high-power LEDs are concentrated in the center of the light. This design results in a bright center area of the outer lens and a less bright perimeter of the outer lens.
Thus, there is a need in the art for a light emitting diode module with improved light distribution uniformity.